Problem: Ashley starts counting at 39, and she counts by fours. If 39 is the 1st number that Ashley counts. what is the 14th number that she counts?
Explanation: What is the first number that she counts? $39$ What is the second number that she counts? $\begin{align*}&39 + 4 \\ &= 43\end{align*}$ What is the third number that she counts? $\begin{align*}&39 + 4 + 4 \\ &= 39 + (2 \times 4) \\ &= 47\end{align*}$ What is the 14th number that she counts? $\begin{align*}&39 + (13\times4) \\ &= 39 + 52 \\ &= 91\end{align*}$